This invention relates to the production of carbamates from a unique combination of materials. More particularly, the invention relates to the production of carbamates from a mixture of reactants, including an oxime.
Carbamates, or urethanes, are useful, for example, in producing isocyanates. Many methods for the production of various carbamates have been disclosed. For example, a primary amine, urea and an alcohol can be reacted to form a carbamate and by-product ammonia. The resulting carbamate can then be thermally decomposed to form the isocyanate.
Isocyanates can be "blocked" by reaction with a material which prevents the isocyanate from reacting at room temperature with compounds that conventionally react with isocyanates, but which allows such isocyanate reaction to occur at a higher temperature. After the isocyanate is formed, it is reacted with the blocking agent to form the blocked isocyanate. The use of such blocked isocyanates is important, for example, in various coating applications. Oximes have been widely reported as effective isocyanate blocking agents. See, for example, "New Developments in the Field of Blocked Isocyanates", by Z. W. Wicks, Jr., Progress in Organic Coatings, 9 pp 3-28, (1981). Isocyanates blocked with such oximes are carbamates, e.g., oxime carbamates.
It would be advantageous to provide a new method for producing such carbamates which does not require the formation of an isocyanate as an intermediate.